Fluid pressure motor



Nov. 27, 1945. A I E 2,389,621

FLUID PRES SURE MOTOR Filed Sept. 16, 1944 5 Sheets-Sheef 3 INVENTOR,

BY r M- ATTORNEYS -iul or compressed air.

tuation or the valve means and-the wasting of compressed air.

More particularly, the invention has for an ob- Q Patented Nov. 27, 1945 2,389,621 rwm raassmm MOTOR Alfred L. Grls, Springfield, Mass, assignor to Gilbert & Barker -Mann!acturing Company, West Springfield, Mass, a corporation of Massachusetts Application September is, 1944, Serial No. 554,405 8 Claims. on. 121-152) This invention relates to improvements in motors of the reciprocating-piston type, adapted to be operated by fluid under pressure.

The invention, while capable of other applications, is especially adapted for-use as a driving means for grease pumps, such for example as are used for delivering lubricant under high pressure into the lubricant fittings, and parts to be lubricated, of an automobile. For such service, it is often necessary to deliver a plurality of charges of lubricant in succession to a lubricant fitting, thus requiring a plurality of cycles of operation of the grease pump. Hence, it is desired to have the motor automatically continue in action for as many strokes oi the grease pump as may be required, an automatically reversing valve means being provided in the motor for the purpose.

A simple reversing valve means for the purpose, and one which is operated solely by pressure or the fluid fed to the motor, is shown in the Wilson and Eagley Patent No. 2,029,145, dated January 28, 1936. This valve means requires the use or a control valve for the compressed air used to operate the valve means andmotor. The operator has to hold this air valve open as well as to control the grease valve in the dispensing nozzle oi the service hose. This is diflicult and inconvenient. Ii one omits the air valve of said patent, the motor can be stopped by closing the valve in the grease nozzle. Since the grease being dispensed is substantially incompressible, stoppage oithe flow of grease will stall the piston or the motor. means of said patent will. continue in operation aiter'the piston is stalled. It the piston stalls anywhere between the two extreme ends of its stroke, pressure will build up in the motor cylinder and cause a reversal so! the valve means and the exhausting oi air from the cylinder.

lest the provision of means, operable by the power piston only at the end of its power stroke, to initiate the reversal of the valve means, the reversal once started being completed by fluid pressure as in said patent.

The invention has for another object the provision of supplementary means, operable by the power piston at the end of its return stroke, to initiate movement of the valve means for the purpose of admitting pressure fluid to the power piston to move the latter on its power stroke, this supplementary means functioning only when the normal means of fluid pressure fails due to sticking of the valve or its pistons.

The invention has for another object to provide the reversing valve means and the valveinitiating-meanaabove desbribed, as a unit secured to the base of the motor independently of the power cylinder and being removable as a unit by simply withdrawing it laterally of the power cylinder after it has been uniastened from the base.

V The invention has for another object the pro- Y vision or a reciprocating-piston, fluid-pressure- However, the reversing valve when the motor cylinder is exhausted, the valve will reverse again andadmit compressed air to the motor cylinder. when the cylinder is filled, as much as possible, pressure again builds up to again cause the valve to reverse and exhaust the cylinder. The described action will continue indefinitely or until the air supply is shut oii 'or rails. The action described is, or course, waste- This invention has for an object the provision of an improved reversing valve or the general type disclosed in said patent but arranged so that the motor may be started and stopped under the. control of the valve in the grease dispensing nozzlewithoutrequiring an v manual control of the compressed air, or other pressure fluid, used to operate the motor and without continuous acconsequent operated motor having generall improved mechanical structure. 1

The invention will be disclosed with reference to the accompanying drawings, in which,

Fig. 1 is a small scale exterior eievational view showing the motor adapted to operate a grease pump, mounted on a cabinet, to dispense grease from a drum contained in the cabinet;

Fig. 2 is a sectional elevational view of the motor and grease pump which it operates;

Fig. 3 is a sectional plan view taken on the line 3-3 ofFig. 2:

Fig. i is a view taken similarly to Fig. 2 but drawn to a larger scale andshowing in more detail the motor and its valve mechanism; and Fig. '5 is an enlarged fragmentary sectional view of a detailshown in Figs. 2 and 4.

Referring to these drawings, the grease pump and its actuating motor are supported from a base plate l (Figs. 1 and 2) which, in this particular case, is mounted on top of a wheeled cabmet 2 (Fig. l) adapted to contain a grease drum it, having its' cover removed. The arrangement is such thatthe grease pump is located in drum 3, near the base thereo! and submerged in the grease, while the motor is exposed outside the cabinet.- a

The grease pump (Fig. 2) consists oi a cylinder 4 within a barrel 8, having threaded on its lower end a casing t, containing a foot valve I, cooperating with a seat 8 formed in the casing. The lower end oi casing O is open to the grease drum andthe upper end, is in communication with the lower end of cylinder 4. Slidable in cylinder I is a piston, comprising. a body 9 packing II and a nut II for clamping the'packing .the body 9 to force valve 32 oil and clamping nut 44. The

.. clamps it to the body. The

to the body. The piston body has an axial passage I2"leading upwardly from its lower end to a valve chamber I3, containing a ball valve I4, adapted to seat on and close the upper end of passage I2. Radial outlets I9 are provided in connect the chamber I3 with the cylinder 4 at a location above the piston packing I0. Secured to the top of the piston is a piston rod I6 which extends upwardly through a conduit I1. The lower end of conduit I1 is threaded into the barrel 5 and the upper end thereof is threaded into the lower end of a hub I8 on a base I9. The hub I8 is mounted in the central axial passage of a hub 20 on. the base plate I with a shoulder on the base I9 resting on th top face of hub 20. 'I'hegrease pump is thus supported from the base plate I and within the drum 3.

The diameter or the piston rod I 6 is less than the internal diameter of. conduit l1, leaving an annular outlet passage 2t, for the grease. This passage, at its upper end; opens into the base of a cylindrical chamber 22. in hub I8. From chamber 22, a radial outlet 23is provided in base I9 having, intermediate its ends, a seat-forming cup 24 for a spring-pressed ball-check valve 25. A nipple 26 connects the outer end of passage 23 to a casing 21. To the upper end of casing 21 is connected the lower element 28 of a swivel joint, the other element 29 being connected to the inner end of a dispensing hose 33. The outer end of this hose customarily carries the usual valve-controlled grease-dispensing nozzle (not shown). 0

The casing 21 has a second' outlet passage 3| normally closed by a spring-pressed ball valve 32. Passage 21 is connected by a radial passage 33 to a tube 34 which extends through baseplate' I and the top wall of cabinet 2 inside the latter in over- I lying relation with the openupper end of grease drum 3. A stem 35, threaded into the lower end of casing 21, may be rotated by handle 36 to its seat and vent the outlet passage and hose 30.. The grease expelled during the venting operation falls into drum 3.

When the piston 9 is lifted, valve 1 opens and valve I4 closes, whereby a partial vacuum is created in the lower end 01' cylinder 4 and valve casing 6 to draw grease therein from drum 3. On the down stroke of the piston, valve 1 closes and valve I4 opens, whereby grease passes through the piston, to be raised ing upstroke thereof. The grease eventually fills the conduit 2I and chamber 22 and is expelled through check valve 25 into the dispensing hose. The actuating motor for the grease pump is of the reciprocating-piston type, actuated by fluid under pressure, such for'example as compressed air. The motor includes a lower large power cylinder 31 and an upper small power cylinder 38, both being formed in coaxial relation in a body 39, secured as by cap screws 40, to the upper face of cylinder 31 is a power piston comprising a body 4I, cupped piston leather 42, backing plate 43 nut 44, threaded on of the piston body piston leather and upper end of piston rod I6 is turned down and threaded as at 45, passing through piston body 4| and threading into the lower end of a connector rod 4 whereby the lower power piston is flxed to the piston rod I6 of the grease pump. This rod 43 is cylindrical, except for its upper end which is'made the upper and smaller part forces plate 43 against the I hexagonal to receive a wrench. The upper pison a succcedthe described base I 9.. In the lower irom a supply pipe 5| to ton consists of a cupped piston leather 41, held between upper and lower circular disks 43 and 49, respectively, by a screw 50, which is threaded into the upper end of rod 46. I

. Pressure fluid, such for example as compressed air. is supplied to the upper end of cylinder 33 a main inlet passage 52, formed in a valve casing 53, secured as by the screws 54 (Fig. 3) to base I 9. Passage 52 is in constant communication with a vertical passage 55 in casing 53. Passage 55 is connected by a compression coupling 56, a metal tube 51 and compression coupling 58 to the upper end of cylinder 33. The upper end ot-this cylinder is thus subjected constantly to air pressure except when the shut-oi! valve (not shown) in supply pipe 5| is closed.

The base IQ forms the head for the lower end of power cylinder 31 and has a chamber 59 therein, which is connected by a lateral conduit 63 in the base to the lower end of valve casing 33. The piston rod I6 enters the chamber 59 through a stuillng box, comprising a hollow casing BI, which is of inverted cup form and is threaded into the bottom wall of the chamber 59 and extends into grease chamber 22. Within this casing are packing rings shaped in cross section, and spreader rings 83. The upper seriesof rings 62 are turned oppositely from the lower series. A spring 64 acting against the upper end of .conduit I1 presses the lower spreader ring 63 upwardly, compressing the lower column of packing rings 62 against the intermediate spreader ring 83, and the latter compressing the upper series of packing rings against the upper and stationary spreader ring 63. The packings 62 are thus expanded against the piston rod I6 and against the peripheral wall of casing BI to prevent the escape of'grease into air chamber 59 or air into grease chamber 22. It will be noted that air leaking from chamber 59 along rod I6 will tend to expand the upper packing rings and that grease,- leaking from chamber 22 along rod I6 will tend to expand the lower set of packing rings. A very eilective seal is thus provided to prevent loss of air and loss of grease.

Referring now to Fig. 4. the air valve casing 53 is provided with upper and lower valve cylinders 65 and 66 of different areas. The upper and smaller cylinder 65 can communicate with air supp y passage 52 by way or horizontal and vertical passages 61 and 68, respectively, the latter opening into the upper end of the cylinder 35. The lower and larger cylinder 36 can communicate with passage ill, and thus with the lower end of the power cylinder 31, by way or a passage 53 formed in a bushing 10, crewed into the lower end of valve casing 53. Slidable in the lower cylinder 68 is a valve piston -1I, having an upper cylindrical extension entering the upper cylinder 65 and to the upper end 12 is clamped by a member 13, threaded into said extension. The upper end of member 13 has a valve 14 to control communication between the passage 83 and cylinder 63. Member 13 ha a diametrical passage 13 therethrough below valve 14 and above valve piston 12, and an axial passage 13 leading from passage 13 downwardly through the member. Fixed to the valve piston H is a valve 11 to control communication between the lower end of valve cylinder 63 and conduit An axial passage 13 extends through this valve 11 and communicates with passage 13. The

upperend oi' valve cylinder 34 is permanently- 62, approximately V- oi. which a piston leather vented to the atmosphere by. a radial passage 19 in casing 53. Below this vent. is larger passage 80 which is closed by piston II when valve" is seated. This exhaust passage 80 communicates with a passage 8| in casing 53. Passage BI is connected by a compression coupling 82 to a tube 83 which extends downwardly through base plate I and the top wall of cabinet 2 into the latter.

The valve 14 has a stem 84, which extends upwardly through passage 68 and through the upper end of the casing 53. A packing ring 85 (Fig.

5), of V-shaped cross section and with its ends skived, is located in a chamber 88 in casing 53 and encompasses stem 84. This chamber 86 is closed by a threaded plug 81 which holds the packing ring in place but which cannot compress it, or move it downwardly, beyond the position shown. The lower Wall of chamber 86 is countersunk, as at 88, to enable any air which passes upwardly along stem 85 to enter the chamber 85 between the two annular parts of the packing ring and force them one against the stem 86 and the other against the peripheral wall of the chamber 86, thereby forming an eifective seal for the stem.

Threaded on the upper end of'stem -84 (Fig. 4)

and therefore adjustable axially on the stem, is'

extend outwardly in opposite directions. The

forked end of arm 93 (Fig. 3) straddles the spool 8t and lies between the end flanges thereof (Fig. 4). The forked end of arm 94 (Fig. 3) straddles the connector 46 and lies in the path of the lower flange 55 (Fig. 4) on the connector 4% and. in the path of the hexagonal flange 96 on the upper end of the connector.

The operation of the valve mechanism will next be described. With the parts positioned as in Fi s. 2 and 4, air under pressure has entered the upper end of the smaller valve cylinder 65 and the difierential valve piston I2, H is held thereby in its lower andillustrated position with the valve ll pressed tightly against its seat on bushing 71W. [is will be clear from Fig. 4, air can then pass through the differential piston, and connected valves, by way of passages It, 16, and 18' and pass out through passage 69 and lateral passage 60 into the lower end 59 of power cylinder at. The air pressure acting on power piston 42 will lift the latter from the position shown in Fig. 2, forcing the smaller power piston 41 upwardly in its cylinder 38; As the large power piston 42 nears the upper end or its power stroke (Fi 4) the flange 95 thereon will engagearm 94, and lift it until its companion arm 93 engages the upper flange of spool 89. A slight additional upward movement of the large power piston will cause the spool 89 and stem 84 to be lifted and the valve 11 raised from its; seat. The action of arms 94, 93 is to crack thevalve 11 off its seat. As soon as this occurs air under pressure enters the lower cylinder 66 from cylinder 31 and drives. the piston ll upwardly against the lesser pressure act- 7 ing downwardly on the smaller piston 12. Air in cylinder 66 above the piston H vents through hole IS. The piston H is instantly driven to its uppermost position, seating valve 14 and stopping inflow of air under pressure to cylinder 65. When piston 1| reaches its upper position, the exhaust passage 80 is fully uncovered andair from any other reason, then the flange to, acting on arm M, will through arm at engage the lower flange oi spool t9 and force stem M downwardly far enough to open valve M. The normal way is for valve Hi to open by air pressure, as first described. The arms 9d, at are provided as a precautionary measure to insure the result if the normal means fail. As soon as valve M opens even slightly, air enters the upper end of cy1inder $5 "and acts on the piston it to drive the latter downwardly as far as it will go, that is until valve ll seats on bushing lid This causes piston H to close off the exhaust passage 80 and also by the closure of valve ll prevents air under pressure from reaching cylinder 66. The

large piston d2 of the air motor is again driven upwardly as described and at the upper end of its stroke the valve ll is again raised to drive the difierential valve piston upwardly, close on. the compressed air supply and allow the upper power piston W to drive the piston rod it downwardly. The action described is repeated indefinitely as long as compressed air supply is turned on and the valve in the grease dispens-- the increasein pressure in the power cylinder.

after the power piston completes its power stroke, or after it is stopped at any point in its power stroke by stoppage of flow of grease from the dispensing conduit. The control of the valve reversal is eilected only by the arrival of the power piston at the end of its power stroke. Then, and only then, will valve ll be opened, the result being efiected by making the power piston mechanically lift the stem at of the reversing-valve-means. Once the valve H is cracked from its seat, pressure fluid rushes into cylinder 66 and rapidly drives the valve means upwardly to cut oil the compressed air supply and open the exhaust passage 80. .The latter is sufficiently restricted to create sumcient back pressure to enable the valve means to be driven all the way up until valve Id closes. The exhaust of the power cylinder is substantially silenced bypiping it into the top of the grease drum-receiving cabinet 2.

It will thus be clear that the motor may be started and stopped in a very convenient manner by the opening and closing of the valve in the T grease dispensing nozzle.

such stroke, the valve," will be closed to prevent 1 reversal of the reversing valve means. If. the

power piston stalls at the end of its power stroke,

the valve means will reverse, exhaust the power cylinder 31 and allow piston 42 to be driven to the end of its return stroke, when the valve means will again reverse to admit fluid pressure to the power cylinder 31 but the piston 42 will remain stalled at the start or its power stroke. If the grease valve is closed during the return stroke of the power piston 42, such stroke will be completed but the power piston will then remain stationary cat the start of its power stroke. Wherever the power piston 42 stops, it is ready for action and becomes immediately enective to dispense grease on opening of the valve in the grease dispensing nozzle.

I claim:

1. A motor, comprising, a power cylinder and a power piston therein, pressure fluid supply means for delivering fluid to one end of said cylinder to move it on its power stroke, yieldable means for moving the piston on its return stroke when said end of the cylinder is connected to exhaust, reciprocating valve means for controlling an alternate supply of fluid to and. exhaust of fluid from said end of said cylinder, means operable by fluid pressure to move said valve means in one direction to admit fluid to said cylinder, means operable by fluid pressure in said cylinder for moving said valve means in an opposite direction to cut oil the supply of pressure fluid and open the exhaust, a valve carried by said valve means to shut 01! communication between the power cylinder and the second fluid-pressure-operated means during the power stroke of the power piston, and means operable by and at the end of the power stroke of said power piston to mechanically liit said valve from its seat and admit fluid pressure from the power cylinder to the second fluid-pressure-operated means and move the valve means to cut oil the supply of pressure fluid to and open the exhaust from said power cylinder. I

2. A motor, comprising, a power cylinder and a power piston therein, pressure fluid supply means for delivering fluid to one end of said cylinder to move it on its power stroke, yieldable means for moving the piston on its return stroke when said end of the cylinder is connected to exhaust, reciprocating valve means for controlling an alternate supply of fluid to and exhaust of fluid from said end of said cylinder, means operable by fluid pressure to move said valve means in one direction to admit fluid to said cylinder, means operable by fluid pressure in said cylinder for moving said valve means in an opposite direction to cut off the supply of pressure fluid and open the exhaust, a valve carried by said valve means to shut oil communication between the power cylinder and the second fluid-pressure-operated means during the power stroke of the power piston, means operable by and at the end 01' the power stroke of said power piston to mechanically lift said valve from its seat to admit fluid pressure fromthe power cylinder to the second fluid-pressure-operated means, and means operable by the power piston at the end of its return stroke to mechanically unseat said valve means if the latter fails to openby fluid pressure.

3. A motor, comprising, a power cylinder, a power piston reciprocable therein, a casing having therein interconnected valve cylinders of different areas, interconnected valve pistons reciprocable in thevalve cylinders, a supply conduit for fluid under pressure smaller valve cylinder, a conduit leading from the opposite end 01' the larger valve cylinder to one end oi the power cylinder, a first valve on the opened and closed, the second valve and said leading to one end of the valve pistons having a passage therethrough opening into the smaller valve cylinder between the smaller valve piston and the first valve, whereby when the flrst valve is open and the second valve closed pressure fluid can pass from the supply conduit to the power cylinder without entering the larger valve cylinder and move the powerv piston in one direction, and means operable by the power piston when it nears the end of its stroke in said direction to initiate the movement of the second valve from its seat, thereby enabling pressure fluid from the power cylinder to enter the larger valve cylinder and acting on the larger valve piston to move the valve pistons to close the flrst valve and open said exhaust passage, and means for moving the power piston in the opposite direction on its return stroke when the exhaust passage is open to exhaust pressure fluid from the said-end of the power cylinder, said valve pistons being movable by pressure fluid from the supply conduit to open the first and close the second valve on completion of the exhausting of said end of the power pylinder.

4. A motor, comprising, a power cylinder, a power piston reciprocable therein, acasing having therein interconnected valve cylinders of diflerent areas, interconnected valve pistons reciprocable in the valve cylinders, a supply conduit for fluid under pressure leading to one end of the smaller valve cylinder, a conduit leading from the opposite end of the larger valve cylinder to one end or the power cylinder, a first valve on the smaller valve piston for opening and closing communication between the supply conduit and the smaller valve cylinder, a second valve on the larger valve piston for opening and closing communication between the larger valve cylinder and the second conduit, the first valve being closed when the second valve is open and vice versa, said larger valve cylinder having an exhaust passage opened and closed by the larger valve piston when the second valve is respectively opened and closed, the second valve and said valve pistons having a passage therethrough opening into the smaller valve cylinder between the smaller valve piston and the flrst valve, whereby when the first valve is open and the second valve closed pressure fluid can pass from the supply conduit to the power cylinder without entering the larger valve cylinder and move the power piston in one direction, means operable by the power piston when it nears the end or its stroke in said direction to initiate the movement of the second valve from its seat, thereby enabling pressure fluid from the power cylinder to enter the larger valve cylinder and acting on the larger valve piston to move the valve pistons to close the first valve and to open said exhaust passage, means for moving the power piston in the opposite direction on its return stroke, when the exhaust e is open to exhaust pressure fluid from thesaid end 01' the power cylinder, said valve pistons being movable by pressure fluid from the supply con duit to open the first and close the second valve on completion or the exhausting or said end of,

the power cylinder, and means operable by the power pistonat the end or its return stroke to open the first valve in the event it does not open automatically by the pressure fluid.

'5. A motor, comprisinga power cylinder, a

power piston reciprocable therein, a casing having therein interconnected valve cylinders of difterent areas, interconnected valve pistons reciprocable in the valve cylinders, a supply conduit for fiuid under pressure leading to one end or the smaller valve cylinder, a conduit leading from the opposite end of the larger valve cylinder to-one end of the power cylinder, a first valveon the smaller valve piston for opening and closing communication between the supply conduit and the smaller valve cylinder, a second-valve on the larger valve piston for opening and closing com-- munication between the larger valve cylinder and the second conduit, the first valve being closed when the second valve is open andvice versa, said larger cylinder having an exhaust passage opened and closed by the larger valve piston when the second valve is respectively opened and closed,

closed, the second valve and said valve pistons having a passage therethrough opening into the smaller valve cylinder between the smaller valve piston and the first valve, whereby when the first valve is open and the second valve-closed Dres-.

sure fluid can pass from the supply conduit to the power cylinder without entering the larger valve cylinder and move the power piston in one direction, and means operable by the power piston when it nears the end of its stroke in said direction to initiate the movement of the second valve from its seat, thereby enabling pressure fluid from, the power cylinder to enter the larger valve cylinder and acting on the larger valve piston to move the valve pistons to close the first valve and open said exhaust passage, a second power cylinder of smaller area than the first power cylinder andconnected to the first power piston, a. continuously open connection from said supply conduit to that end of the second power cylinder opposite to the first-named end or the first power cylinder, whereby when the latter is connected to exhaust the second power Piston the secondyalve and said valve pistons having a passage therethroiigh opening intothe smaller valve cylinder between the smaller valve piston and the first valve, whereby when the first valve is open andthe second valve closed pressure fluid can pass from the supply conduit to the power cylinder without entering the larger valve cylinder and move the power piston in one direction, me'ans operable by the power piston when it nears the end of its stroke in said direction to initiate the movement of the second valve from its seat, thereby enabling pressure fluid from the will eflect the return stroke of the first power piston, said valve pistons being movable by the pressure fluid to open the first and close the second valve on completion or the exhausting or the sec- 7 ond power cylinder, and means operable by the first power piston at the end of its return stroke for initiating the opening of the first valve in the event that it i'ails to open automatically by power cylinder to enter the larger valve cylinder and acting on the larger valve piston to move the valve pistons to close the first valve and to open said exhaust passage, a second powercylinder oismaller area than the first power cylinder,

a second power piston reciprocable in the second power cylinder and connected to the first power piston, a continuously open connection fromsald suppl conduit to that end or the second power cylinder opposite to the first-named end of the ing therein interconnected valve cylinders of dii-,

ferent areas, interconnected valve pistons reciprocable in the valve cylinders, a supply conduit for fiuid under pressure leading to one end of the smaller valve cylinder, a conduit leading irom the opposite end of the larger valve cylinder toone end of the power cylinder, a first valve on the smaller valve piston for opening and closing communication between supply conduit and the smaller'valvecylinder, a second valve on the larger valve piston for opening and closing communication between the larger valve cylinder and the second conduit, the first valve being closed when the second valve is open and vice versa, said larger cylinder having an exhaust passage opened and closed by the larger valve piston when the'second valve is respectively opened and fiuid pressure.

7. A motor, comprising, a base, a power cylinder mounted on said base, a power piston reciproca'ble in said cylinder, a valve casing having a valve chamber, said casing being mounted on said .base and removable independently of the power cylinder, the base having a passage interconnecting the adjacent ends of the power cylinder and valve chamber, valve means reciprocable in said chamber and havingv avstem extending out of the casing in parallel relation with the axis of the power piston, and a lateral actuating connection for said stem extending from said stem into the path of the power piston; said valve casing, valv, stem and lateral connection being removable laterally as a unit on disconnection of the valve casing from the base.

8. Amotor, comprising, a base, a power cylinder mounted on said base, and having a lateral .opening therein, a power piston reciprocable in said cylinder, a valve casing having a valve chamher, said casing being mounted on said base and removable therefrom independently or the power cylinder, the base having a passage interconnect ing the adjacent ends of the power cylinder and valve chamber, valve means reciprocable in said chamber and having a stem extendingout of the casing in parallel relation with the axis of the power piston, a guide on said casing parallel ing said stem, a member slidable on said guide and connected to move said stem, said member extending laterally into'said opening and cylinder and having an inner forked end straddling said piston rod, and an abutment on the piston rod for engaging and moving said member at a predetermined point in the stroke of thepower piston; said valve casing, stem, guide and member being withdrawable as a unit laterally from the cylinder and base on disconnection of the easing from the base. h

- ALFRED women. 

